Intracellular restriction factors in mammalian cells--An ancient defense system finds a modern foe.

Cross-species transmission of retroviruses poses a threat to mammalian species. Zoonoses have given rise to devastating diseases because the host organism is not prepared to resist a new pathogen. Mammals have developed several layers of defense against viruses, including an intracellular antiretroviral defense, a part of innate immunity. Retroviral restrictions had been studied for decades using murine leukemia virus in mice, however it has become clear that primates too have intrinsic mechanisms to ward off infections by retroviruses. Several of these antiretroviral restriction mechanisms have recently been identified, with two particularly well described factors being members of the tripartite motif (Trim) and APOBEC families. Both systems provide a strong barrier against lentiviral infections. The viruses have developed countermeasures that allow them to replicate despite the host factors. This review discusses our current knowledge of this ancient battle between mammalian hosts and their retroviral opponents.

Monthly administration of a continuous erythropoietin receptor activator provides efficient haemoglobin control in non-dialysis patients during routine clinical practice: results from the non-interventional, single-cohort, multicentre, SUPRA study.

BACKGROUND: The continuous erythropoietin receptor activator (C.E.R.A.) has a long half-life, a relatively low binding affinity for the erythropoiesis receptor and low systemic clearance. These characteristics permit once-monthly dosing, which could reduce staffing requirements and be advantageous for patients. However, outcomes observed during controlled trials of C.E.R.A. have not been assessed under everyday clinical conditions in which physicians make all therapeutic decisions based on their own experience, rather than according to a pre-defined protocol. OBJECTIVE: This study aimed to assess whether the efficacy and safety of C.E.R.A. reported during controlled trials are reproducible under routine clinical conditions. METHODS: This was a non-interventional, single-cohort, multicentre study carried out in 92 specialist nephrology clinics and private practices in Germany. The study included patients with non-dialysis chronic kidney disease and anaemia, with or without current erythropoiesis stimulating agent (ESA) therapy. C.E.R.A. initiation and dosing was at the discretion of the physician. The primary efficacy variable was the proportion of patients for whom all measured haemoglobin (Hb) values during months 7-9 were within the range 11-12 g/dL ('responders'). RESULTS: 335 patients received ≥1 dose of C.E.R.A.; 150 had previously received ESA therapy. The mean number of doses was 7.6 per patient over a mean follow-up of 7.9 months. Mean ± SD Hb was 10.7 ± 1.1 g/dL at baseline and 11.3 ± 1.1 g/dL at the final visit (efficacy population, n = 205). The primary endpoint, all measured Hb values during months 7-9 within the range 11-12 g/dL, was achieved by 19.0% (39/205) of patients, increasing to 41.5% for Hb 11-13 g/dL, 42.0% for 10-12 g/dL and 76.6% for Hb ≥10 g/dL. Hb fluctuation during months 7-9 was ≤1 g/dL in 185/205 patients (90.2%). C.E.R.A. was well tolerated without novel safety concerns. CONCLUSION: Hb levels remained stable during routine use of C.E.R.A. in an unselected population of non-dialysis chronic kidney disease patients with anaemia. C.E.R.A. was administered approximately monthly compared with 3-7 doses per month on previous ESA therapy.

The RING-type ubiquitin ligases Pex2p, Pex10p and Pex12p form a heteromeric complex that displays enhanced activity in an ubiquitin conjugating enzyme-selective manner.

The RING finger peroxins Pex2p, Pex10p and Pex12p are central components of the peroxisomal matrix protein import machinery. The RING domain enables each of these proteins to exhibit ubiquitin-protein ligase activity, which has been linked to ubiquitin-dependent regulation of the peroxisomal import receptor Pex5p. The RING peroxins are considered to form a heteromeric complex in vivo, although the elucidation of the structural assembly, as well as the functional interplay of the RING domains, has remained elusive. Using in vitro approaches, we show that the RING domains form a heteromeric complex with Pex10p(RING) as a central component that directly binds the Pex2p(RING) and Pex12p(RING). The RING domains proved to function as heteromeric pairs that display an Pex10p-dependent enhanced ligase activity in an ubiquitin conjugating enzyme-selective manner.

Murine T cells potently restrict human immunodeficiency virus infection.

Development of a mouse model for human immunodeficiency virus type 1 (HIV-1) infection has advanced through the progressive identification of host cell factors required for HIV-1 replication. Murine cells lack HIV-1 receptor molecules, do not support efficient viral gene expression, and lack factors necessary for the assembly and release of virions. Many of these blocks have been described using mouse fibroblast cell lines. Here we identify a postentry block to HIV-1 infection in mouse T-cell lines that has not been detected in mouse fibroblasts. While murine fibroblastic lines are comparable to human T-cell lines in permissivity to HIV-1 transduction, infection of murine T cells is 100-fold less efficient. Virus entry occurs efficiently in murine T cells. However, reduced efficiency of the completion of reverse transcription and nuclear transfer of the viral preintegration complex are observed. Although this block has similarities to the restriction of murine retroviruses by Fv1, there is no correlation of HIV-1 susceptibility with cellular Fv1 genotypes. In addition, the block to HIV-1 infection in murine T-cell lines cannot be saturated by a high virus dose. Further studies of this newly identified block may lend insight into the early events of retroviral replication and reveal new targets for antiretroviral interventions.